CN107079127A - Projector and image display method - Google Patents

Abstract

The projector (1) includes: an image processing unit (10) for performing image processing on an input image signal; an image display element (22) for receiving the image signal processed by the image processing unit and generating an optical image; and a projection optical system (23) for projecting the optical image generated by the image display element onto a projection surface. The image processing unit (10) includes an image correction unit (12) for reducing blur of an image projected by the projection optical system (23), and the image correction unit (12) changes the black brightness level of the image signal.

Description

Projector and image display method

technical field

The present invention relates to a projector and a method of displaying an image by projecting and displaying an image on a projection surface, and particularly relates to a technique for appropriately reducing blurring of a projected image.

Background technique

Generally, a projector is installed on a horizontal surface such as a table or a ceiling, and projects an image onto a screen installed on a vertical surface such as a wall. In this case, adjust the posture and the like of the projector so that a clear image can be projected on the screen.

However, not all projectors can be set so that the setting plane and the screen plane are in a perpendicular relationship. For example, in the case of installation in a stepped wide auditorium, since a projector installed on the ceiling projects onto a screen at the front of the auditorium in a plan view, the image is distorted into a trapezoidal shape. In addition, although portable projectors used in conference rooms etc. often project from a table, they may not necessarily be able to project onto a vertical wall surface, and similarly often display distorted images. The method of adjusting so as to have a rectangular shape without this distortion is keystone correction (keystone correction). In keystone correction, a trapezoidal image is converted into a rectangular image by performing a geometric transformation operation such as reduction or enlargement on the projected image signal.

In the case of the above-mentioned keystone correction, the resolution is partially lowered especially in downscaling, so geometric blurring occurs. As a method for improving this geometric blur, sharpness processing is mentioned. In connection with this, Patent Document 1 discloses a technique for reducing geometric blur in enlarging and reducing operations during keystone correction by sharpness processing. Specifically, it is described that a screen is divided into a plurality of regions, an adjustment value for sharpness adjustment is set for each divided region, and the sharpness adjustment of each region is performed based on the adjustment value.

Patent Document 1: Japanese Patent Laid-Open No. 2011-77971

Contents of the invention

The lens of the projector is designed to be uniformly focused on the screen if the distance to the screen and the angle of projection are appropriate (hereinafter referred to as reference setting). However, when the projector and the screen are set out of the reference setting and keystone correction is performed, the image in the portion of the image within the rectangle that exceeds the depth of field of the lens is blurred due to focus shift. That is, even if keystone correction is performed, the range in which an appropriate image can be obtained is significantly limited. Also, even with the standard setting, there is a problem that if the design or precision of the lens is not appropriate, blurring will occur at the edge of the screen mainly due to the difference in projection distance from the center of the screen and aberrations.

Blurring caused by a difference in throw distance when keystone correction is performed is particularly noticeable in ultra-short throw projectors and wide-angle short-throw projectors in which the projection angle becomes steep at the screen edge of a projected image. In addition, recently, not only projection onto a flat surface such as a screen or a wall, but also projection onto a three-dimensional object including a curved surface such as a building called projection mapping is often performed. In projection onto a three-dimensional object, there is a problem that a difference in focal length occurs due to depth, and thus blurring occurs due to focus shift when there is a distance difference greater than or equal to the depth of field.

With the sharpness correction employed in Patent Document 1, such blurring due to focus shift exceeding the depth of field cannot be completely resolved. This is because the sharpness correction can improve the spatial resolution of the video signal, but cannot improve the optical resolution such as the focus shift of the projection optical system of the projector.

In view of the above problems, the present invention provides a projector and an image display method that appropriately reduce image blur caused mainly by the resolution of a projection optical system, such as lens focus shift.

The present invention is a projector for displaying an image by projecting it on a projection surface. The projector is characterized in that it includes: an image processing unit for performing image processing on an input image signal; The image signal processed by the image processing part generates an optical image; and the projection optical system projects the optical image generated by the image display element onto the projection surface, and the image processing part has an image correction part for reducing the To blur the projected image, the black luminance level of the image signal is changed in the image correction unit.

In addition, the present invention is an image display method for displaying an image by projecting it on a projection surface. The image display method is characterized by comprising: an image processing step of performing image processing on an input image signal; an optical image generation step, The image signal that has been image-processed is input, and an optical image is generated by an image display element; and the projection step uses a projection optical system to project the generated optical image to a projection surface. The image correction function that changes the black brightness level of the image signal due to the blurring of the projected image.

According to the present invention, it is possible to appropriately reduce image blur caused by the resolution of the projection optical system, such as lens focus shift.

Description of drawings

FIG. 1 is a diagram showing the configuration of a projector in Embodiment 1. As shown in FIG.

FIG. 2 is a diagram showing the configuration of a video correction unit in FIG. 1 .

FIG. 3 is a diagram illustrating the relationship between a focal point and a real image by a convex lens.

FIG. 4A is a diagram showing the principle of projecting an image in a projector.

FIG. 4B is a diagram illustrating blurred images generated by the projector.

FIG. 5 is a graph showing a Gaussian distribution.

FIG. 6 is a graph showing LoG distribution (second order differential of Gaussian distribution).

FIG. 7A is a diagram illustrating a method of correcting video signals in Embodiment 1. FIG.

FIG. 7B is a diagram showing a state where blurring occurs without correction.

FIG. 7C is a graph showing the effect of offset and gain adjustments.

FIG. 8A is a diagram illustrating an example of a blur-reduced menu display.

FIG. 8B is a diagram showing an example of a menu display for brightness adjustment.

FIG. 9A is a diagram illustrating an example of input-output characteristics obtained by adjusting brightness individually.

FIG. 9B is a diagram illustrating an example of input-output characteristics of brightness adjustment linked to a blur reduction function.

FIG. 10 is a diagram showing the configuration of a video correction unit in Embodiment 2. FIG.

FIG. 11 is a diagram showing the configuration of a video correction unit in Embodiment 3. FIG.

FIG. 12 is a graph showing PSF data at each lens position.

FIG. 13 is a diagram showing the configuration of a video correction unit in Embodiment 4. FIG.

FIG. 14 is a diagram showing the configuration of a video correction unit in Embodiment 5. FIG.

FIG. 15 is a graph showing PSF data under lens movement.

FIG. 16 is a diagram showing the configuration of a video correction unit in Embodiment 6. FIG.

FIG. 17A is a diagram showing an example of an internal image of a projector (without keystone correction).

FIG. 17B is a diagram showing an image obtained by projecting the image in FIG. 17A with an elevation angle added to the optical axis of the projector.

FIG. 18A is a diagram showing an example of an internal image of a projector (with keystone correction).

FIG. 18B is a diagram showing an image obtained by projecting the image in FIG. 17A with an elevation angle added to the optical axis of the projector.

FIG. 19A is a ray diagram when projected from a projector to a projection plane perpendicular to the optical axis.

FIG. 19B is a ray diagram when projected from a projector with an elevation angle θ added to the optical axis.

FIG. 20 is a diagram showing a case where the video correction unit is configured by an external video device.

(Symbol Description)

1: projector; 2: screen (projection surface); 3: external image device; 10: image processing unit; 11: input signal processing unit; 12, 30: image correction unit; 13: timing control unit; 20: optical components ;21: light source (lamp); 22: liquid crystal panel (LCD); 23: lens; 31: position acquisition unit; 32: geometric calculation unit; 33: blur amount calculation unit; 34: resolution restoration unit; 35: brightness conversion Section; 36: Core Computing Section; 37: PSF Mapping; 38: Histogram Acquisition Section.

detailed description

Hereinafter, although embodiment of this invention is described based on drawing, this invention is not necessarily limited to these embodiment. In addition, in each drawing explaining an embodiment, the same member is attached|subjected to the same code|symbol, and the overlapping description is abbreviate|omitted.

Example 1

In Embodiment 1, a projector that performs resolution restoration processing using an inverse diffusion process operation will be described.

FIG. 1 is a diagram showing the configuration of a projector in Embodiment 1. As shown in FIG. The projector 1 includes: a video processing unit 10 that takes broadcast waves or a video input signal 100 output from a PC as input, and processes the video signal; and an optical component 20 that inputs a display control signal 103 to a liquid crystal panel as a video display element, The projected video 203 is generated and projected on the screen 2 serving as a projection surface to be displayed.

The image processing section 10 includes: an input signal processing section 11, which is input with an image input signal 100, and converted into an internal image signal 101 through, for example, a decoder for compressing image signals, IP conversion, a scaler, keystone correction, etc.; an image correction section 12, the internal video signal 101 is input, and converted into the corrected video signal 102 by performing resolution restoration processing based on the inverse diffusion process calculation described later; The horizontal and vertical synchronization signals are used to generate the display control signal 103 .

The optical component 20 includes: a light source (lamp) 21 that generates illumination light 201; a liquid crystal panel (LCD) 22 as an image display element that receives a display control signal 103 output from the image processing unit 10 and adjusts the illumination light 201 for each pixel. and the lens 23 as the projection optical system adjusts the focus of the optical image 202 generated by the liquid crystal panel 22 to project the projection image 203 onto the screen 2 .

Furthermore, the projector 1 has a function of displaying a menu screen for the user to perform operations such as adjustment of the brightness (brightness), contrast, color tone, keystone distortion, etc. of the projected image, switching of input signals, etc., and is configured to On the other hand, the function of each part is controlled by the control part which is not shown in figure.

FIG. 2 is a diagram showing the configuration of the video correction unit 12 in FIG. 1 . The image correction unit 30 (corresponding to the symbol 12 in FIG. 1 ) includes: a position acquisition unit 31, which acquires a pixel position 301 consistent with the input signal in the projection optical system from the optical component 20 to the screen 2; a geometric calculation unit 32, which calculates When each pixel in the image signal is projected onto the screen 2 through the lens 23, the position 302 where the image light crosses on the lens; the blur amount calculation part 33 calculates the blur amount 303 according to the position 302 on the lens; and the resolution restoration part 34, Inverse diffusion calculation is performed based on the internal video signal 101 and the blur amount 303 .

The geometric calculation unit 32 calculates the position 302 where light rays intersect on the lens using the Gaussian imaging formula based on the pixel position 301 on the LCD 22 and the distance of the optical axis estimated by the set focal length and zoom. When a is the distance from the object to the lens, b is the distance from the lens to the real image, and f is the focal point, the Gaussian imaging formula is expressed by Equation 1.

[Formula 1]

FIG. 3 is a diagram illustrating the relationship between a focal point and a real image by a convex lens. As shown in the figure, when the focal point f of the lens 40 and the position a of the object 41 are given, the distance b to the real image 42 is determined using Equation 1. In the case of a projector, object 41 is an image on LCD 22 , and real image 42 is an image projected on screen 2 .

FIG. 4A is a diagram showing the principle of projecting an image in a projector. Regarding the video image of the projector 1 , the illumination light generated by the lamp 21 passes through the LCD 22 to form a video image. Using the focal length and zoom function of the lens 23 , the image is formed so as to match the size and position of the screen 2 . In the LCD image 51 in the drawing, a point P1 is displayed at the center of the screen. This point P1 is imaged as a point P2 on the screen 2 like a screen image 52 . At this time, when the screen 2 is within the range of the depth of field D, no image blurring will be felt.

FIG. 4B is a diagram illustrating blurred images generated by the projector. When the screen 2 is outside the range of the depth of field D, the point P1 of the LCD image 51 is imaged as an extended point P2' on the screen 2 like the screen image 52'. This causes blurred images.

Here, imaging blur in a camera will be described. For example, imagine an image that causes a focus shift in a digital camera. Light passes through the lens of a digital camera, diffuses due to focus shift, and becomes a blurred image when it reaches a CCD (Charge Coupled Device, Charge Coupled Device) imaging element.

A method of restoring such a blurred image will be described. When the actual input image (original image) is set as I _o (x, y), the blurred image taken is set as I(x, y), and the blurring process is set as K ^t , use Equation 2 to express their relationship. Here, the process of blurring expressed by Equation 2 is called a diffusion process.

[Formula 2]

I(x, y) = K ^t I _c (x, y)

The photographed blurred image I(x, y) is restored to an actual image (original image) through the diffusion process of Retrospective Equation 2. This relationship is expressed by Equation 3, and the process of retrospectively tracing the diffusion process is called the reverse diffusion process.

[Formula 3]

I ₀ (x, y) = K ^-1 I(x, y)

There are several methods for solving the inverse diffusion process. For example, a function obtained by functionalizing a distribution spread like point P2' in FIG. 4B is called a point spread function (PSF: Point Spread Function). When this PSF is P(x, y), the diffusion process becomes Equation 4.

[Formula 4]

Here, the operation of the PSF and the video signal is referred to as a convolution product, and the convolution product of the function f(x, y) and the function g(x, y) is generally expressed as in Equation 5.

[Formula 5]

Focusing on expressing by multiplication when performing Fourier transform on the convolution product, it becomes Equation 6 when performing Fourier transform on both sides of Equation 4.

[Formula 6]

The underline in the formula represents the Fourier transform. The original actual image I ₀ (x, y) can be obtained by performing inverse Fourier transform after dividing Equation 6 by P(x, y) (overlined).

As another method, there is a method using a Gaussian distribution. FIG. 5 is a graph showing a Gaussian distribution, and the irradiance distribution of light such as a general pinhole exhibits a characteristic of a Gaussian distribution with respect to the optical axis. When the diffusion process K ^t of Equation 2 follows the Gaussian distribution G _t (x, y), Equation 2 becomes Equation 7.

[Formula 7]

Here, the multiscale decomposition (Mulitisscale Decomposition) processing (Q.Li, Y.Yoshida, N.Nakamori, "A Multiscale Antidiffusion and Restoration Approach for Gaussian Blurred Images", Proc. IEICETrans.Fundamentals, 1998), the actual image I ₀ (x, y) is decomposed as in Equation 8.

[Formula 8]

The second-order differential of the Gaussian distribution in the formula is called LoG (Laplacian of Gaussian, Laplacian of Gaussian), and expressed as in Formula 9. In addition, FIG. 6 is a diagram showing LoG distribution.

[Formula 9]

Furthermore, when the standard deviation σ, which is the scale in the Gaussian distribution, is substituted into Equation 8 according to Equation 10, the inverse diffusion process becomes as in Equation 11, and the actual image I ₀ (x, y) can be obtained.

[Formula 10]

σ _n+1 ＝κσ _n ＝κ ⁿ σ ₁

[Formula 11]

As described above, the method of restoring a blurred image represented by a convolution product is called deconvolution (Deconvolution), and it is effective for restoring image blur in a camera.

Next, restoration of a blurred image in the projector 1 will be described. In the case of a camera, a diffusion process caused by focus shift of a lens is included in a photographed image signal, but in the case of a projector, a diffusion process is performed by a lens after converting the image signal to an optical system.

Therefore, assuming the corrected image obtained by the image correcting unit 30 as I _C , the diffusion calculation K ^t of the lens in the optical system is completed, and the result is an ideal image I ₀ without blurring projected on the screen. That is, their relationship is expressed as in Equation 12.

[Formula 12]

I ₀ (x, y) = K ^t I _c (x, y)

Here, the image input to the projector is I ₀ , so I _C must satisfy Equation 13.

[Formula 13]

I _c (x, y) = K ^-t I ₀ (x, y)

This is equivalent to the operation when I(x, y) is set to I ₀ (x, y) in Equation 3. That is, in the resolution restoration unit 34 of the image correction unit 30, the inverse diffusion process calculation K ^-t is performed on the original image I ₀ (x, y) in advance, so that the blur caused by the focus shift of the projected image 203 can be reduced. However, the inverse diffusion process calculation K ^-t is overcorrection for an ideal image without blur, so a negative value is generated in the signal level. In response to this negative value, correction using gain α and offset β is introduced as described later.

The correction method by the video correction unit 30 will be described with reference to FIGS. 7A , 7B, and 7C.

FIG. 7A is a diagram illustrating a method of correcting video signals in Embodiment 1. FIG. In this figure, the input image I ₀ input to the image correction unit 30, the corrected image I _C from the image correction unit 300, and the projected image I _S on the screen 2 are shown when the input image I ₀ is set as a point image. The brightness level at the horizontal position.

The graph of the corrected image _{IC shows the luminance level calculated by Equation 13, and the graph of the projected image I S shows} the luminance level obtained by superimposing the Gaussian distribution (that is, the PSF) of the estimated blur ratio on the corrected image _IC . If the corrected image I _C calculated in this way can be realized, it is possible to obtain a projected image I _S with a luminance distribution close to that of the input image I ₀ .

FIG. 7B is a diagram showing a state where blurring occurs without correction for comparison. The graph of (a) shows the brightness distribution (brightness level) of the image 51 input to LCD22 in FIG. 4B. This image has not been corrected by the image correction unit 30, so it is equal to the input image I ₀ . The graph in (b) shows the luminance distribution (luminance value) of the blurred image 52 ′ projected on the screen 2 in FIG. 4B . The luminance value on the screen 2 is a value measured by a surface luminance meter or the like. In this way, the input image 51 on the LCD 22 expands into a Gaussian distribution on the projected image 52 ′ on the screen 2 , resulting in blurring.

In addition, the corrected image I _C calculated by Equation 13 includes negative values in the luminance level as shown in FIG. 7A . However, when the video signal is converted to an optical system, the negative value of the video signal cannot be expressed using the intensity of light. Therefore, correction of gain α and offset β is introduced as in Equation 14, thereby expressing a high dynamic range and negative correction. When this is shown in FIG. 7A , the luminance level distribution on the vertical axis is shifted to the positive side by an offset β, so that the luminance level takes only positive values. In addition, the gain is adjusted by α so as to match the original brightness level.

[Formula 14]

FIG. 7C is a graph showing the effects of offset and gain adjustments at the time of correction. The graph in (a) shows the brightness level of the image 51' input to the LCD 22, that is, the corrected image _IC . Regarding the input corrected image signal I _C , the black luminance level for expressing negative values is increased by the offset β, and the gain α is adjusted to match the white luminance level.

The graph in (b) shows the luminance distribution (luminance value) of the image 52 (projection image I _S ) projected on the screen 2 . On-screen blur is reduced by corrections that include inverse diffusion operations. In this case, by introducing offset and gain adjustments, there is an effect that an image with an increased black luminance value and a high dynamic range can be obtained.

The resolution restoration unit 34 in FIG. 2 performs inverse diffusion calculation based on Equation 14. In addition, the blur amount calculation unit 33 obtains the blur amount as a standard deviation when the diffusion process follows a Gaussian distribution. As for the standard deviation, it is also possible to measure the PSF on the optical axis with a surface luminance meter at the position where focus shift occurs as shown in FIG. 4B, or to obtain the PSF on the optical axis from the optical characteristics of the lens, and calculate The projection distance is approximated by linear interpolation. The above is the method of reducing image blur in a projector.

Next, an example in which the blur reduction function of this embodiment is added to the menu function of the projector will be described. As the menu function of the projector, for example, the brightness, contrast, color tone, keystone adjustment, input switching, etc. of the setting screen are used for the user to select and set.

FIG. 8A is a diagram illustrating an example of a blur-reduced menu display. For example, the name of this function is set to "blur removal" 61, and several options are set. When the ideal value of the gain α in Equation 14 is set to a, and the ideal value of the bias β is set to b, the blur reduction function is activated (ON) when the option is “Strong”, and this When the offset β is set to the ideal value b, and the gain α is set to 1/(a+b). In addition, in the case of "medium", β=0.5b, α=1/(a+b+0.5b), and in the case of "weak", β=0.25b, α=1/(a+b+ 0.75b). In the case of "OFF", the blur reduction function is disabled (OFF). Accordingly, the user can execute the blur reduction function at a desired level according to the type of video and the projection environment.

Next, it is also possible to link the blur reduction function with other image processing functions, and an example of linking with brightness adjustment will be described with reference to FIGS. 8B, 9A, and B. Brightness is a function to adjust the brightness of the screen image, and the adjustment can be "brighten" or "dark". This adjustment includes a method of adjusting (dimming) the luminance value of the light source, and a method of adjusting the luminance level by video signal processing without changing the luminance of the light source. Here, the latter method of adjusting the brightness level by video signal processing will be described.

FIG. 8B is a diagram showing an example of a menu display for brightness adjustment. For example, let the name of this function be "brightness" 62, and the adjustment level of brightness usually has plus or minus, and as an example, it can be adjusted stepwise from +30 to -30. The brightness level of the video signal is also changed during brightness adjustment.

FIG. 9A is a diagram illustrating an example of input/output characteristics of a video signal whose brightness is individually adjusted. That is, it is a case where the blur reduction function in FIG. 8A is disabled (blur removal=“OFF” is selected). β' in the figure represents the brightness adjustment level, which is set by the adjustment level in Fig. 8B. (a) is a case where the brightness is adjusted in a positive direction, that is, a direction that brightens an image, and (b) is a case where the brightness is adjusted in a negative direction, that is, a direction that makes an image darker. Regarding these adjustments, for the brightness adjustment level β', the relationship of output luminance level=input luminance level+β' holds true.

FIG. 9B is a diagram illustrating an example of input-output characteristics of brightness adjustment linked to a blur reduction function. That is, it is a case where the blur reduction function of FIG. 8A is activated (blur removal=“strong”, “medium”, or “weak” is selected). In this case, the output brightness level is determined by linking the offset value β used in the video signal correction in FIG. 7A and the brightness adjustment level β' in FIG. 9A .

(a) is linked to the brightness adjustment β' in the positive direction, but the brightness adjustment and the blur reduction function are processed in the same way, so in order to avoid repeated application, the larger value of β' and β is used. . That is, β is adopted when the offset value β is greater than the brightness adjustment level β', and conversely, β' is adopted when β' is greater than β. (b) is a case of interlocking with the brightness adjustment β' in the negative direction, but in order to perform the blur reduction function, the offset value β is preferentially used. In either case of (a) and (b), the offset value β becomes the lower limit value for brightness adjustment.

The control unit of the projector appropriately switches and executes the functions of the brightness adjustment described above and the brightness adjustment linked with the blur reduction function according to the user setting status of the menu functions.

The brightness adjustment has been described above as an example, but the same applies to, for example, the contrast adjustment of a video, that is, the slope adjustment of an input-output line. That is, if the contrast adjustment level α' is greater than the gain value α of this embodiment, α' is used, and if the gain value α of this embodiment is greater than the contrast adjustment level α', then α is used. That is, the gain value α in this embodiment becomes the lower limit value of the contrast adjustment level.

According to the configuration of the first embodiment, it is possible to provide a projector that can appropriately reduce image blur caused by lens focus shift.

Example 2

In Embodiment 1, the configuration of a projector provided with resolution restoration processing by inverse diffusion calculation was described. In Embodiment 2, a structure for improving the precision of the dediffusion calculation is further described by matching the luminance level correction of the image signal calculated based on the dediffusion process with the luminance value after the application of the projection optical system, that is, the illumination luminance value.

FIG. 10 is a diagram showing the configuration of the video correction unit 30 ( 12 ) of the projector in the second embodiment. This is a configuration in which a luminance conversion unit 35 is added to FIG. 2 of the first embodiment.

In addition to the position acquisition unit 31 , the geometric calculation unit 32 , and the blur amount calculation unit 33 , the video correction unit 30 further includes a brightness conversion unit 35 that converts the brightness level from the internal video signal 101 to the effective brightness signal 305 . The resolution restoration unit 34 performs inverse diffusion calculation using the blur amount 303 and the effective luminance signal 305 .

In the luminance conversion unit 35 , a conversion table is used to convert the luminance level from the internal video signal 101 to the effective luminance signal 305 . For example, the conversion table is created based on the optical characteristics (such as gamma characteristics) of the lamp 21 and the LCD panel 22, or by measuring all the gradations of R, G, and B with a luminance radiation spectrophotometer or the like.

Here, it is assumed that the conversion calculation from the internal video signal 101 to the illumination luminance value is L. In the resolution restoration unit 34 , L-inverse transformation is performed on the internal video signal 101 in order to calculate the inverse diffusion calculation and the diffusion effect by the lens using the same characteristics. This becomes the conversion table described above. As a result, an arithmetic expression obtained by adding the inverse transformation L ^-1 of L to Equation 14 is Equation 15.

[Formula 15]

According to the configuration of the second embodiment, in a projector having a large difference between an internal video signal and irradiation luminance due to gamma characteristics or the like, it is possible to improve the accuracy of reducing image blur caused by lens focus shift.

Example 3

In the third embodiment, a configuration in which the accuracy of the inverse diffusion calculation is improved by tabulating the blur amount of the lens in the configuration of the first embodiment will be described.

FIG. 11 is a diagram showing the configuration of the video correction unit 30 ( 12 ) of the projector in the third embodiment. In FIG. 2 of the first embodiment, a kernel calculation unit 36 and a PSF map 37 are added instead of the blur amount calculation unit 33 .

The image correction unit 30 includes, in addition to the position acquisition unit 31 and the geometric calculation unit 32, a PSF map 37 prepared in advance according to the optical characteristics based on the lens position; 307 performs interpolation, and outputs it as a blur amount 303 . The resolution restoration unit 34 performs inverse diffusion calculation using the internal video signal 101 and the blur amount 303 .

In Embodiment 1, a convex lens is taken as an example. The premise is that the light parallel to the optical axis crosses at the focal point after passing through the lens, so the blurring of the image is caused by the focus shift. However, there are aberrations in the actual lens, so sometimes the light does not converge to the focal point, such as expanding into a circle in the case of spherical aberration. Aberrations include Seidel's five aberrations and chromatic aberrations, which cause smearing and color shift at positions away from the optical axis.

Here, based on the design data of the lens, it is possible to precalculate or observe blurred information, that is, a spot map. Therefore, the PSF at each lens position is mapped to the data table in advance (PSF map 37 ).

Among them, the coefficients are mapped to the data table for the part that can be functionalized, and the convolution kernel is mapped as it is for the part with complex characteristics. However, when storing this information at pixel positions on all lenses, the amount of data increases, so for example, if there is symmetry, the symmetric part is deleted. In addition, as shown in FIG. 12 , data may also be thinned out by performing linear interpolation based on intersection points of the center and the vertex, and the horizontal axis, the vertical axis, and each side of the rectangle. In addition, when the chromatic aberration is large, the PSF calculated for each wavelength of R, G, and B may be used.

When data is thinned out by performing linear interpolation as described above, the PSF map 37 in FIG. 11 stores a data table in which PSFs are mapped, and the thinned-out data is interpolated by the kernel calculation unit 36 . In addition, Equation 4, that is, Equation 6 based on the Fourier transform may be used for calculating the PSF in the resolution restoration unit 34 .

According to the configuration of the third embodiment, it is possible to improve the accuracy of reduction of image blur caused by lens aberration.

Example 4

In Embodiment 4, a case where aperture adjustment and lamp brightness adjustment are added to the configurations of the above-described embodiments, and a case where dynamic control is performed using video histograms will be described.

FIG. 13 is a diagram showing the configuration of the video correction unit 30 ( 12 ) of the projector in the fourth embodiment. Here, the histogram acquisition unit 38 is further provided in addition to the configurations of the second embodiment ( FIG. 10 ) and the third embodiment ( FIG. 11 ), and an adjustment value 310 for aperture adjustment and lamp brightness is input.

The video correction unit 30 includes a position acquisition unit 31, a geometric calculation unit 32, a kernel calculation unit 36 that outputs a blur amount 303 using a PSF map 37, and a luminance conversion unit 35 that converts an internal video signal 101 into an effective luminance signal 305. It includes a histogram acquisition unit 38 that acquires a histogram of the internal video signal 101 and outputs histogram information (frequency information) 308 , and also receives an adjustment value 310 for aperture adjustment and lamp brightness. The resolution restoration unit 34 receives, in addition to the blur amount 303 and the effective luminance signal 305 , the histogram information 308 of the video signal, the aperture adjustment value, and the lamp brightness adjustment value 310 , and performs inverse diffusion calculation.

Specifically, the resolution restoration unit 34 decreases the α value and β value in Eq. In this way, the dynamic range is given priority to avoid blurring caused by the weakened contrast of the image. Conversely, when reducing the F value by aperture adjustment or increasing the light intensity by brightness adjustment, increase the α value and β value in Equation 15 to give priority to the blur reduction function by the inverse diffusion calculation.

In addition, regarding the histogram information of video, when the frequency of black-and-white two-color and high-contrast two-color is high, there are many cases of video for presentations composed of characters and figures, so the expression 15 is enlarged α and β values. Conversely, when the input image is evenly distributed in halftone, it is often an image such as a photograph, so the overall contrast is prioritized by reducing the α value and the β value.

According to the structure of the fourth embodiment, the parameters of the inverse diffusion calculation can be dynamically set by using the adjustment of the aperture, the brightness of the light, and the histogram information of the image, so that the image blur can be effectively reduced.

Example 5

In Embodiment 5, a case where dynamic control is performed by lens movement adjustment in the configurations of the above-described embodiments will be described.

FIG. 14 is a diagram showing the configuration of the video correction unit 30 ( 12 ) of the projector in the fifth embodiment. Here, the configuration of the second embodiment ( FIG. 10 ) and the configuration of the third embodiment ( FIG. 11 ) are further input with the image display position information 311 based on lens movement.

The image correction unit 30 has: a position acquisition unit 31; a geometric calculation unit 32; a kernel calculation unit 36 connected to the PSF map 37 and receiving image display position information 311 based on lens movement; Transformation is performed to an effective luminance signal 305 . Here, the kernel calculation unit 36 interpolates the calculated convolution kernel 307 using the PSF map 37 and the image display position information 311 based on the lens shift, and outputs it as the blur amount 303 . The blur amount 303 and the effective luminance signal 305 are input to the resolution restoration unit 34, and the inverse diffusion calculation is performed.

In the third embodiment (FIG. 11 and FIG. 12), the spot map, which is blurred information, is calculated in advance from the lens design data or observed, and the PSF at each lens position is stored in the PSF map 37 . In the case of performing lens shift adjustment in this embodiment, for example, as shown in FIG. 15 , a PSF map 37 including the lens shift range is prepared, and the PSF of the intersection of the center and the vertex, the horizontal axis, the vertical axis, and the side is used to limit the image display The range is linearly interpolated.

According to the configuration of the fifth embodiment, it is possible to improve the accuracy of reduction of image blur caused by lens movement.

Example 6

In Embodiment 6, a case where keystone correction (keystone distortion correction) is performed in the configurations of the above-described embodiments will be described.

FIG. 16 is a diagram showing the configuration of the video correction unit 30 ( 12 ) of the projector in the sixth embodiment. Here, the setting value 312 of the keystone correction is also input to the configurations of the second embodiment (FIG. 10) and the third embodiment (FIG. 11).

The image correction unit 30 has: a position acquisition unit 31; a geometric calculation unit 32, which receives the set value 312 of the trapezoidal correction; a kernel calculation unit 36, which uses the PSF map 37, and outputs a blur amount 303; Signal 101 is transformed into effective luminance signal 305 . Here, the geometric calculation unit 32 calculates the distance to the screen and the distance ratio to the optical axis using the set value 312 of the trapezoidal correction, and calculates the position where the image rays intersect on the lens (reference number 302 ). The resolution restoring unit 34 is input with the blur amount 303 and the effective luminance signal 305, and performs inverse diffusion calculation.

First, correction of keystone distortion in a projected image will be described using FIGS. 17 and 18 .

FIG. 17A shows a case where keystone correction is not performed in an example of the internal image 71 of the projector 1 . When the keystone correction described later is not performed, an image having the same rectangular shape as the input image signal 100 is formed on the liquid crystal panel 22 . FIG. 17B shows an image 72 obtained by projecting the internal image 71 in FIG. 17A onto the screen 2 by adding an elevation angle to the optical axis of the projector 1 . In this case, the image 72 on the screen 2 becomes a shape in which the upper portion expands into a trapezoidal shape and stretches upwards, and so-called trapezoidal distortion occurs.

Therefore, in the input signal processing unit 11 , in order to suppress the occurrence of trapezoidal distortion, the input video signal 100 is reduced in the vertical direction of the video and geometrically transformed into a trapezoidal video opposite to the screen video. This correction is called keystone correction or keystone distortion correction. Set the correction amount of keystone correction according to the size of keystone distortion.

FIG. 18A shows a case where keystone correction is performed on an example of the internal image 73 of the projector 1 . In the rectangular image 73 , the trapezoidal area 73 a is the original image, and the hatched area 73 b at the end is no signal (black). FIG. 18B shows an image 74 obtained by projecting the image 73 in FIG. 18A onto the screen 2 by adding an elevation angle to the optical axis of the projector 1 . Here, although the projected image 74 has a trapezoidal shape, the hatched area 74b at the end is invisible because there is no signal. Therefore, on the screen 2, the original video is displayed in the rectangular area 74a.

FIG. 19A is a ray diagram when projected from the projector 1 to the projection surface 2 perpendicular to its optical axis. It is assumed that, in the case of projection onto the vertical projection surface 2 , light is properly projected without trapezoidal distortion. FIG. 19B is a ray diagram when projected from the projector 1 with an elevation angle θ added to its optical axis. In the projection surface 2' to which the elevation angle θ is added, it can be seen that the distance between the light rays is wider and the projection distance is longer as it goes upward.

From the above relationship, it can be estimated how much the projection surface (screen) 2 is tilted by the setting of the keystone correction. The geometric operation part 32 is inputted with the setting value 312 of the trapezoidal correction, calculates the distance to the screen 2 and the distance ratio to the optical axis, and uses it to calculate the distance between the pixels in the image signal and the projection of the light through the lens 23 to the screen 2. Position 302 of the upper cross.

In the third embodiment (FIG. 11 and FIG. 12), the spot map, which is blurred information, is calculated in advance from the lens design data or observed, and the PSF at each lens position is stored in the PSF map 37 . In the present embodiment, the core calculation unit 36 superimposes on the PSF the PSF calculation of the focus shift using the distance difference to the screen 2 , for example, performing linear interpolation.

According to the configuration of the sixth embodiment, it is possible to improve the accuracy of reduction of image blur caused by keystone correction.

According to each of the above-described embodiments, it is possible to appropriately reduce image blur caused by the resolution of the projection optical system, such as the focus shift of the lens. Thereby, there is an effect that image blurring when performing keystone correction, projection mapping, etc. is appropriately reduced, and even a projected image having a distance difference greater than or equal to the depth of field can be clearly displayed.

In addition, in each embodiment, the description was made based on the configuration of the projector as shown in FIG. 1, but as shown in FIG. connect.

Each of the above-described embodiments is an example described in detail to explain the present invention in an easy-to-understand manner, and is not limited to an example having all the described configurations. In addition, it is also possible to replace part of the structure of a certain example with the structure of another example, or to add the structure of another example to the structure of a certain example. In addition, addition, deletion, and replacement of other configurations can be performed on part of the configurations of the respective embodiments.

In addition, in the above embodiments, a projector has been described as an example, but the present invention is also effective in projection optical system devices such as head-mounted displays and head-up displays having similar components in principle.

Claims (14)

1. A projector that projects an image onto a projection surface to display, the projector is characterized in that it has: The image processing unit performs image processing on the input image signal; an image display element that is input with an image signal subjected to image processing by the image processing unit to generate an optical image; and a projection optical system for projecting an optical image generated by the image display element onto the projection surface, The video processing unit has a video correction unit for reducing blur of the video projected by the projection optical system, and the black brightness level of the video signal is changed in the video correction unit. 2. The projector of claim 1, wherein: The video processing unit also has a function of changing the black brightness level of the video signal in order to adjust the brightness of the video, The projector includes a control unit that displays a menu screen for a user to set a state of an image displayed on the projection surface, and controls the image processing unit based on user operations, The menu screen includes: a first setting item for setting ON and OFF of the operation of the image correction unit in order to reduce the image blur; and setting a black brightness of the image signal for adjusting the brightness. The second setting item of the grade, The control unit switches between the first state and the second state according to user setting states of the first setting item and the second setting item, wherein, The first state is a state in which the black luminance level is not changed accompanying the operation of the video correction unit when the first setting item is off, and the second setting item to change the black brightness level, The second state is a state in which the change of the black luminance level accompanying the operation of the video correction unit and the black color based on the second setting item are changed in a state where the first setting item is ON. In conjunction with the change of the brightness level, the black brightness level of the video signal is changed. 3. The projector according to claim 1 or 2, characterized in that, The image correction unit has: a blur amount calculation unit that calculates a blur amount of an image generated on the projection surface when each pixel in the image signal is projected onto the projection surface through the projection optical system; and The resolution restoration unit performs an inverse diffusion process operation on the input image signal, thereby reducing image blur and restoring resolution. 4. The projector of claim 3, wherein: When performing the inverse diffusion process calculation, the resolution restoring unit adds an offset to the black brightness level, which is a value of 0 in the brightness level, in order to express the negative value of the video signal, and adjusts it to match the original white brightness level. Gain for the brightness level. 5. The projector of claim 3, wherein: The video correction unit includes a brightness conversion unit that converts a brightness level from an input video signal to an effective brightness signal based on the optical characteristics of the video display element and a light source that supplies illumination light to the video display element, The resolution restoration unit performs the inverse diffusion process calculation on the effective luminance signal converted by the luminance conversion unit. 6. The projector of claim 3, wherein: The blur amount calculation unit stores blur amounts generated due to aberrations of lenses constituting the projection optical system in a data table, and performs data interpolation using the data table to calculate blur amounts at each pixel position. 7. The projector of claim 4, wherein: The resolution restoration unit is input with an aperture adjustment value of a lens constituting the projection optical system and a brightness adjustment value of a light source, and reduces the black brightness level added to the video signal when the amount of irradiated light decreases. bias. 8. The projector of claim 4, wherein: The video correction unit includes a histogram acquisition unit that acquires a histogram of the input video signal, The resolution restoring unit increases the black brightness level of the video signal when the frequency of black and white or the frequency of high-contrast binary values is high based on the histogram information from the histogram acquisition unit. Added bias. 9. The projector of claim 6, wherein: The image display position information obtained by lens shift adjustment of the lens is input to the blur amount calculation unit, and the blur is stored in the data table so as to include an image display range moved by the lens shift adjustment. amount of data. 10. The projector of claim 3, wherein: The image correction unit includes a geometric calculation unit that receives a keystone correction setting value for correcting trapezoidal distortion of an image projected on the projection surface, and calculates the keystone correction setting value using the keystone correction setting value the distance to the projection surface and the distance ratio to the optical axis, and calculate the position where the image light rays intersect on the lens in the projection optical system, The blur amount calculation unit calculates the blur amount based on a calculation result of the geometric operation unit. 11. A method for displaying an image, projecting an image onto a projection surface for display, the method for displaying an image is characterized in that it has: An image processing step, performing image processing on the input image signal; an optical image generating step of inputting the image signal subjected to the image processing, and generating an optical image using an image display element; and a projecting step of projecting the generated optical image onto the projection surface using a projection optical system, In the image processing step, there is an image correction function of changing the black brightness level of the image signal in order to reduce the blur of the image projected by the projection optical system. 12. The image display method according to claim 11, wherein: In the image processing step, there is also a function of changing the black brightness level of the image signal in order to adjust the brightness of the image, The video display method includes a control step of displaying a menu screen for a user to set a state of a video displayed on the projection surface, and controlling the video processing step according to user operations, The menu screen includes: a first setting item for setting ON and OFF of the operation of the image correction function in order to reduce the image blur; and setting a black brightness of the image signal for adjusting the brightness. The second setting item of the grade, Switching between the first state and the second state according to the user setting state of the first setting item and the second setting item, wherein, The first state is a state in which, in a state where the first setting item is off, the change of the black brightness level accompanying the operation of the image correction function is not performed, and the second setting item to change the black brightness level, The second state is a state in which the change of the black luminance level accompanying the operation of the image correction function and the black level based on the second setting item are changed in a state where the first setting item is ON. In conjunction with the change of the brightness level, the black brightness level of the video signal is changed. 13. The image display method according to claim 11 or 12, wherein: Among the image correction functions: a blur amount calculation step of calculating a blur amount of an image generated on the projection surface when each pixel in the image signal is projected onto the projection surface through the projection optical system; and The resolution restoring step is to perform an inverse diffusion process operation on the input image signal, thereby reducing image blur and restoring resolution. 14. The image display method according to claim 13, wherein: In the resolution restoration step, when performing the inverse diffusion process calculation, an offset is added to the black luminance level which is a value of 0 in the luminance level in order to express the negative value of the video signal, and in order to be different from the original white luminance level Adjust the gain to match the brightness level.